injury causes fragmentation of the axon and myelin sheath

schwaan cells become reactive and proliferate

macrophages phagocytose debris

nerve fibres reconnect with end organs and are remyelinated by schwaan cells

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Why does Wallerian degeneration fail in the CNS

inflammation myelin debris is not completely removed glial scar is formed by reactive astrocytes astrocytes

regrowth of axons is inhibited by myelin debris and glial scar

a cystic cavity forms

lack of growth promoting molecules and an inhibitory environment

may have reactive end bulbs

oligodendrocytes > myelin debris astrocytes > glial scar

55

describe reactive astrocytes after injury

hypertrophy expression of inhibitory molecules and normal molecules which forms a glial scar which the axon cannot pass through

56

where are glial cells segregated into CNS or PNS

glial limiting membrane at the dorsal root entry zone

57

what is the substantia gelatinosa

a mass of gelatinous gray matter that lies on the dorsal surface of the dorsal column and extends the entire length of the spinal cord into the medulla oblongata and transmits painful sensory information.